The objectives are to study the properties and mechanism of action of enzymes involved in the biosynthesis of lactose. These are UDP-glucose Pyrophosphorylase, UDPglucose-4-Epimerase and "Lactose Synthetase" which consists of two proteins: alpha-lactalbumin and galactosyltransferase also involved in the transfer of galactose to glycoproteins. The chemical and physical properties of these enzymes will be studied. A proposed intermediate in the UDPgalactose-4-epimerase reaction has been identified as UDP-D-xylo-4-ketosulose. The role of tyrosyl will be examined in both alpha-lactalbumin and galactosyltransferase. The carbohydrates units in galactosyltransferase will be isolated and sequenced as will the carbohydrate units in glyco-alpha-lactalbumin.